On July 8th, Duckworks owner Chuck Leinweber let me know Frank Smoot (from diy-tris.com) had just released building plans for a new small trimaran. Frank calls this new boat the “Slingshot 16.”
If you’re a regular reader of this site, then you’ll already know we’ve previously featured Frank’s boats in posts such as this one. Frank has learned a lot about small tris in a really short period of time. He is a really fast boatbuilder too!
Chuck was very impressed with these new building plans. He wrote, “…they are really as complete and precise set of plans as I have ever seen.”
About a day after I heard from Chuck L., SmallTrimarans reader Tom Williams sent me the following info after purchasing a set of these plans (he gave me permission to share his comments):
“Frank Smoot, of DIY TRIS, who you have highlighted previously, finally made very very detailed plans for his 16 ft trimaran, plans now known as slingshot 16. I have purchased plans today and am very impressed. Comes as an instant download/pdf. Construction manual =78 pages, drawings= 58 pages. Super duper detail on those drawings. He said that he spent alot of time getting these perfect, as he has purchased alot of plans that seemed lacking. I can tell you having purchased plans from 2 other well known designers that these are the best I have ever seen.”
Tom has started a blog in order to share details and pictures of the building of his boat here: http://slingshot16.blogspot.com/
You can read the short bio about Frank at Duckworks here…
http://www.duckworksbbs.com/plans/smoot/index.htm
And here is the info page about the building plans for the new Slingshot 16 trimaran design…
http://www.duckworksbbs.com/plans/smoot/slingshot16/index.htm
Anyone interested in purchasing a set of plans for this boat may do so at the link above.
I am a great admirer of Frank’s work; we’ve also had some correspondence in previous years.
However, on a 16 ft boat I’d rather be able (not an obligation, but a chance) to carry along a friend, or a child, or even a dog or cat, and have them sitting to my side :-)
There’s enough space Frank, let’s go for it ! Let’s have a slingshot double ! :-)
cheers for all your projects, Stefano
Thanks for your kind words, Stefano. To respond to your message, I will very soon be releasing plans for my 19-footer, which will hold 2 or more people. I’ll let Joe know as soon as they are available.
Take care – Frank
Hi Frank! I just stumbled on your site. I am also a closet small tri junkie. I’ve been toying with the idea of using surf boards for amas. Any thoughts?
Hi Phil – I have never done it, but I think you should give it a try and see what you discover.
Cheers – Frank
Phil, been done before. A while back by an English woman I think. Search Google she might have actually used old windsurfers. Cut them along the centre and used either side.
Hi Tony (love the last name, btw)!
What I didn’t make clear is to use whole, very small surfboards, including fins, laying flat on the water just as if you were standing on the board. My theory is that as soon as you pick up a little speed the board will plane and offer a tremendous amount of lift/stability while still being able to pierce waves. My hope is that by canting the inside edge down slightly it will also aid in upwind effort like you were initiating a turn. Stay tuned!
Hi Phil,
Having surfed for near on 35 years the surfboard concept will work but only to a limit.
Frank has experimented with various AMA designs with flatter bottoms to induce a planing effect. Depending on many variables I think his overall conclusion is that they slap a lot more and induce vibration depending on wave frequency.
Have a look at the WR16 AMA design, they have a wave piercing nose and then flatten out at the mid going to the back so that as speed increases they offer a planing surface for added lift over displacement.
The problem you might encounter with a surfboard as an AMA is the dreaded nose dive effect. Having encountered a few steep drop in’s on waves over the years they do bury with enough momentum, the board wants to stop whilst whatever is attached to it (surfer or boat) wants to keep going. I would imagine with rigid AKA connections that this would put a lot of strain on them.
What you could try is to copy a Hawaiian outrigger AMA design in foam core with a strong stringer (wooden bit down the middle). They like the WR16 wave pierce at the bow and then broaden to plane.
The main thing to remember is that AMA’s encounter many various wave directions from the front predominantly but also from the rear in a following sea.
On my little tri which is an 11′ Bazooka I was considering some new AMA’s. But the more I though it through regarding volume, shape and overall design the more I saw just how well designed the existing ones where.
They are symmetrical in design which basically means the same shape at the front as the back so that when fitted it makes no difference to performance.
Wave piercing ends broadening to a full round mid section. No flat planing surface but the main hull essentially is very flat and planes which pulls them along the surface like they are planing. It’s an easy to balance boat with simple hiking out on the tramp so that the leeward AMA is not immersed too heavily.
If you get hit by a big gust the AMA design will submerge, but being essentially torpedo shaped they just missile through the water with a drag increase that slows you down gradually and allows you to spill wind from the main and hike out further to counter the strong gust.
In a heavy squally we got hit by a 35knt gust, 1 man out on either side and one child in the front. AMA sunk on the leeward side and induced a short jibe which further filled the sail and drove us harder into it. The AMA simply torpedoed through the water as we had time to shift our weights and counteract the forces.
So what i’m essentially saying is that these little outrigger thingy’s actually do a lot more than just float. There are many variables involved in what they encounter and depending on what you want to achieve your design will need to adapt to these or suffer / benefit in other ways.
A planing design like a surfboard will work, but it will also change the dynamic of what you are doing and accordingly things like performance, sea kindliness, and handling as well as induced loads across the entire boat.
If it’s not a big job and you have some old boards around have a crack at it. Otherwise it might be cheaper to put something like Wesley’s expandacraft outriggers on instead. http://expandacraft.com/
Also as a side thought the fins on the board may be too far towards the rear and mess up the rudder loads a bit as the boat tries to pivot around them with the sail loaded. (The sail wanting to turn the boat with the wind, and the fins resisting at the rear act like a pivot).
The Expanda’s look like a good general design and are very adaptable. But you could likely build some ply AMA’s a lot cheaper.
Hi Tony,
Thanks for that excellent information. I do worry about the slapping, but having windsurfed for 35 years ?, I am not too concerned about pearling, at least in protected waters. I had not considered open waters with large swell or a following sea, but my sailing is going to be mostly lakes or some place like South Padre Island. I may still give it a go and will share if I do!
Cheers